The present invention relates to a semiconductor device, a process for production thereof, and electronic equipment.
CSP (chip size package) to cope with increase in the number of electrodes in recent semiconductor chips has been usually accomplished by pellet-bonding the semiconductor chip and wire-bonding the semiconductor chip to the wiring of the wiring substrate side. FIG. 14 is a sectional view showing an example of the semiconductor device of wiring bonding type. In this figure, a is a polyimide resin base, b is a wiring film, c is an electrode forming hole, d is a micro ball electrode of solder formed in said electrode forming hole c, 1 is, for example, a silver paste film, f is a semiconductor chip which is bonded to the surface of the base a through the silver paste film 1, i is a resin reinforcement and a ring to dam up resin, m is a wire to electrically connect the electrode of the semiconductor chip f and the wiring film b, and n is a sealing resin supplied by potting.
However, CSP (chip size package) of the type in which the semiconductor chip is flip-chip-connected has recently appeared.
FIG. 15 is a sectional view showing one of conventional examples of CSP of flip chip connection type which employs FPC (flexible printed circuit board). In this figure, a is a polyimide resin base, b is a wiring film of copper formed on the surface of said base a, c is an electrode forming hole formed in said base a, d is a micro ball electrode of solder formed in said electrode forming hole c, e is an anisotropic conducting film, i is a film-reinforcing ring of, for example, copper or nickel, j is an adhesive to bond the film-reinforcing ring i to the base a, and k is a plating film of gold that coats the surface of said wiring film b. The anisotropic conducting film e bonds the semiconductor chip f to the base a surface and it also connects the external lead electrode of said semiconductor chip f to the wiring film b through the metal bump g on said electrode surface.
By the way, since CSP of the type shown in FIG. 14 is constructed such that the semiconductor chip f is mounted on the base a with its electrodes upward and the electrodes are connected to the wiring film b by means of the wire m, the bent part of the wire m is above the top of the semiconductor chip f and there was the problem that it is difficult to reduce the thickness of the sealing resin and in turn to reduce the thickness of the package.
By contrast, CSP of the type shown in FIG. 15, which does not use the wire m, has no such a problem. However, there is an increasing demand for high integration and miniaturization of semiconductor devices, and there was a problem that it is difficult to meet the requirement for further smaller and thinner packages. One reason for this is that the package of the type shown in FIG. 15 has the wiring film b which is formed on the surface of the resin base a. In other words, the wiring film b makes the resulting package thicker by its thickness, and hence it is difficult to meet the requirement for further thickness reduction.
Moreover, since the wiring film is formed convex on the film surface, the resin hardly enters the gap between the wiring film and the wiring film, and voids are liable to occur. These voids absorb moisture and absorbed moisture explodes at the time of reflowing, thereby peeling the connection between the wiring film on the film and the bump.
The present invention was completed in order to solve such problems. It is intended to facilitate the production of a semiconductor device of CSP or BGA type, in which the chip is mounted in flip chip type, to reduce cost, to reduce the package thickness, and to improve reliability.
The semiconductor device of the first claim is characterized in that it includes a wiring substrate and a semiconductor chip, said wiring substrate having a wiring film and an insulating resin formed thereon such that the former is embedded in one surface of the latter, with one surface of the former being flush with said one surface of the latter, said wiring substrate further having a hole at the position where at least part of said wiring film overlaps with said insulating resin, said semiconductor chip having at least part of its external lead electrodes connected to said wiring film on said wiring substrate through bumps.
Therefore, according to the semiconductor device of the first claim, since the wiring film is embedded in one surface of the base, it is possible to eliminate steps on the surface, and further since the semiconductor chip is mounted by flip chip on such base surface, it is possible to reduce the thickness of the semiconductor device.
And, since it is possible to form the electrode forming hole by exposure and development, it is possible to contrive miniaturization and higher integration density, and in turn it is possible to increase integration of the semiconductor device and to increase the number of electrodes.
The production process of the semiconductor device of the thirteenth claim is characterized in that it includes the steps of providing a wiring substrate which is so formed as to permit a plurality of semiconductor chips to be mounted thereon and a plurality of semiconductor chips each having bumps formed on the external lead electrode, connecting the gap between said bump of said each semiconductor chip and the wiring film of said wiring substrate by ultrasonic wave or heating under pressure, casting a resin into the vicinity of said bumps, thereby sealing it, and finally separating said wiring substrate to give a plurality of semiconductor devices.
Therefore, according to the production process of the semiconductor device of the thirteenth claim, the semiconductor chip is flip-chip-connected to the wiring substrate by ultrasonic wave or by heating under pressure and sealed with a resin, and subsequently it is divided; therefore, it is possible to obtain simultaneously a plurality of semiconductor devices which have been made thin.
The production process of the semiconductor device of the fourteenth claim is characterized in that it includes the steps of providing a wiring substrate and a plurality of semiconductor chips mounted thereon, each having bumps formed on the external lead electrode, pasting an anisotropic conducting film to the wiring film forming plane of said wiring substrate, placing the semiconductor chip on said anisotropic conducting film on said wiring substrate, electrically connecting the gap between the bump of said semiconductor chip and said wiring film by heating under pressure, and casting a resin into the vicinity of said semiconductor chip for its sealing.
Therefore, according to the production process of the semiconductor device of the fourteenth claim, the semiconductor chip is flip-chip-connected to the wiring substrate by using the anisotropic conducting film, and sealing with a resin, thereby it is possible to obtain the semiconductor device which has been made thin. Also, since the substrate is flat, voids hardly occur and it hardly suffers breakage due to moisture absorption at the time of reflowing.
The semiconductor device of the fifteenth claim is characterized in that a plurality of wiring films are placed on one side of an insulating resin base such that the surface of said wiring film is approximately flush with the surface of said base and at least part of said wiring film is so formed as to overlap with the electrode forming hole in said base, said electrode forming holes are filled with a conducting material, external electrodes projecting toward the opposite side of the wiring film are formed, and the semiconductor chip is flip-chip-bonded to said one surface of said base.
Therefore, according to the semiconductor device of the fifteenth claim, since the wiring film is embedded in one surface part of the base, it is possible to eliminate surface steps; since the semiconductor chip is mounted on such a surface, the mounting of the semiconductor chip becomes easy, and it is possible to increase the reliability of the semiconductor device. And, since the electrode forming hole can be formed by exposure and development, it is possible to contrive miniaturization and increased integration, and in turn it is possible to contrive higher integration of the semiconductor device and increase in the number of electrodes.
And, in the case where a metal ring is bonded outside the flip chip connection part on the base on which the wiring film is formed, the ring functions as a gland source and also as an electrostatic shield to shield the semiconductor chip electrostatically from outside. The ring also functions as a dam to prevent the sealing resin from leaking outside at the time of resin sealing.
The semiconductor device of the sixteenth claim is characterized in that a plurality of wiring films are placed on one side of a base having electrode forming holes such that the surface of said wiring film is approximately flush with the surface of said base and at least part of said wiring film is so formed as to overlap with the electrode forming holes, said electrode forming holes are filled with a conducting material, external electrodes projecting toward the opposite side of the wiring film are formed, a semiconductor chip is bonded with its reverse side to said one side of said base by means of the insulating film, and each electrode of said semiconductor chip is flip-chip-connected to its corresponding wiring film.
Therefore, according to the semiconductor device of the sixteenth claim, the wiring film is embedded in one side of the base and hence it is possible to eliminate surface steps; since the semiconductor chip is mounted on such a surface, flip chip connection of the semiconductor chip becomes easy, and it is possible to increase the reliability of the semiconductor device. And, since the electrode forming hole can be formed by exposure and development, it is possible to contrive miniaturization and higher density of integration, and in turn it is possible to contrive higher integration of the semiconductor device and increase in the number of electrodes.
The production process of the semiconductor device of the twenty-first claim is characterized in that it includes the steps of selectively forming a masking film on one side of a metal substrate, forming a wiring film by plating through said masking film, forming an etch-stopping metal film as an underlayer, forming an insulating resin base having electrode forming holes on the surface adjacent to the wiring film of said metal substrate, and performing etching on the reverse side of the region in which at least the wiring film is formed on said metal substrate such that at least the etch stopping metal film constituting said underlayer is exposed.
Consequently, according to the production process of the semiconductor device of the twenty-first claim, it is possible to form a wiring film by plating which employs the metal substrate as a masking film and subsequently form the electrode forming holes of insulating resin and form the external electrodes by plating; therefore, it is possible to easily form the wiring film and external electrodes by electroplating. The reason for this is that since the metal substrate and each wiring film are in the electrically connected state, it is possible to impart a potential necessary for electroplating to the entire surface of the metal substrate. And, since it is possible to obtain by electroplating a plating film with better film quality than that obtained by electroless plating, it is possible to easily obtain a good wiring film and external electrode. And, therefore, it is possible to reduce the size of the wiring film and external electrode and increase the density of wiring density. And, coupled with the size reduction of the wiring film, it is possible to increase the number of wiring film that can be passed between the external electrodes, and in turn it is possible to increase the number of arrangement tiers of the external electrode. This makes it possible to increase the number of external electrodes.
Also, since it is possible to form the electrode forming hole by pattering of the insulating resin on the metal substrate, it is possible to reduce the size of the electrode forming hole. It became possible to reduce the diameter of the electrode forming hole to 0.22 mm or below, which conventionally could not be reduced below 0.5 mm for FPC type or below 0.35 mm for rigid substrate type. And, coupled with the reduction in size of the electrode forming hole, it is possible to increase the density of arrangement of the electrode forming holes. Since it is possible to form the electrode forming hole by patterning the insulating resin, working is not troublesome but is highly productive unlike the conventional practice in which the electrode forming hole is made by drilling as in the case of rigid substrate.
And, the etching is performed on the region in which at least the wiring film is formed on the metal substrate until the etch stopping metal film constituting at least said underlayer is exposed from the reverse side. This etching is performed such that the outer metal substrate remained in the form of a ring. In this way it is possible to use the remaining part as a ring. And, it is possible to use the ring as the gland source terminal and electrostatic shield as mentioned above. Since this ring forms the external shape of the semiconductor device and it is formed by etching, it is possible to improve working precision. Therefore, it is possible to improve the external shape precision of the semiconductor device.
Moreover, since production is carried out by using the metal substrate as a base metal, there is no possibility of deformation such as bending during production. Therefore, it is easy to carry out working even though the semiconductor device becomes large. Consequently, it is possible to easily increase the size of the semiconductor device.
The electronic equipment of the twenty-third claim is characterized in that it contains at least one of the semiconductor devices defined in the first to twelfth claims and the fifteenth to twentyth claims.
Therefore, according to the electronic equipment of the twenty-third claim, since the semiconductor devices having the above-mentioned advantages are used, it is possible to enjoy their advantages.